Buildings are often built with transparent glass windows to allow natural sunlight into the building and to afford its occupants a "view of the outside". Windows are aesthetically pleasing for these reasons. Unfortunately, heat is relatively easily transferred through glass windows. This heat transfer increases the costs for heating and air conditioning the building. This, of course, is not desirable.
Storm windows have long been recognized as one solution for decreasing heat transfer through a glass window. Normally, a storm window is mounted on the outside of the building in front of the regular, permanently installed window, e.g. a double hung window with movable sashes, contained in the wall of the building. Besides adding an additional layer of glass, storm windows create an air space in front of the regular window which acts as insulation. Storm windows usually comprise a transparent glass pane of approximately the same size as the regular window mounted in some type of frame. Some storm windows must be removed and installed each year. Other storm windows, of the so-called "triple track type", are permanently installed and represent a slidable glass pane. The glass pane can be slid down to function as a storm window or slid up during the summer with a screen being slid down in its place.
The conventional storm windows noted above have various disadvantages. They are relatively expensive since they comprise a solid glass pane of approximately the same size as the normal window. They are relatively heavy which makes them hard to remove or install if they are of the removable type. In addition, the permanently installed storm windows of the triple track type are exactly what that name implies. They are permanently mounted on the outside of the building and to some degree obstruct the view, especially the screen portions of the unit.
Various storm windows have been proposed comprising flexible plastic sheets which may be wound up onto a spring roller. These sheets may be unrolled when use of a storm window is desired and placed in front of the regular window. Various types of sealing means are employed in an attempt to seal the flexible plastic sheet against air infiltration. When the storm window is not needed or not desired, the sheet is wound up onto the spring roller and can be easily hidden from view. Therefore, it does not have the disadvantages of permanently mounted storm windows.
Many of the prior art storm windows made from flexible plastic sheets have various disadvantages. Some of these disadvantages relate to the means used to seal the plastic sheets against air infiltration. For example, U.S. Pat. Nos. 2,361,762 and 2,009,917 disclose devices of this type where felt weatherstripping is used to seal the flexible plastic sheets in their frames. However, the weatherstripping is not used around all four sides of the plastic sheet and is therefore not totally effective. Moreover, felt weatherstripping is easily degradable and may soon become unsuitable for acting as an effective sealing medium. This requires replacement of the felt weatherstripping which is, of course, undesirable.
Other prior art devices disclose various mechanical systems for sealing the plastic sheets in their frames. For example, U.S. Pat. No. 2,847,064 discloses manually inswishes to use the storm window. U.S. Pat. No. 2,769,491 discloses a vertically movable latch bar having a plurality of pivotal tabs which can be moved into engagement for clamping against the plastic sheet. Such an arrangement is, however, unduly complex and expensive.